The head-and-neck tumor is a tumor developing in e.g., the ears, nose, pharynx, larynx, cervical region or oral cavity. In particular, a malignant tumor thereof is mostly found in males of 50 years old or older and represents 6% of all malignant tumors. The morbidity increases with age and 650,000 or more people are afflicted over the world and 350,000 of them die of the disease (malignant tumor). Among them, larynx cancer is a malignant tumor most commonly developed in the head and neck. The future forecast of annual death tolls estimates that the number of deaths will increase (see Non-patent Document 1).
A head-and-neck tumor is diagnosed based on staging performed using endoscopic inspection and various image inspections (CT, MRI, PET, etc.) and tissue diagnosis by means of biopsy. In the case of a benign tumor diagnosed based on these, a primary radical resection enabling a complete cure is performed; whereas, in the case of a malignant tumor, an operation, radiation therapy and chemotherapy are performed. In the case of advanced cancer, a combination therapy of them must be required. However, an operation for a head-and-neck tumor gives significant cosmetic damage to the head and neck and the face, and in addition, highly affects physical functions such as vocalization and swallowing. Because of significant physical and psychological invasion, patient's QOL (Quality of Life) significantly decreases. In addition, a therapeutic effect of combination therapies of these is not always high and thus a 5-year survival rate in advanced cancer remains at most about 30% (see Non-patent Document 2).
MicroRNA is a single-stranded RNA having a length of about 22 bases, present within a cell and not translated into a protein (see Non-patent Document 3). MicroRNA was found in C. elegans in 1993, also in a vertebrate animal in 2001 and conserved beyond species. At present, it is estimated that nearly 1000 microRNAs are present on a human genome and so far 800 or more human microRNAs have been cloned. Furthermore, microRNA presumably controls a gene by binding to mRNA in 30% of the protein coding region on a genome (see Non-patent Document 4). Therefore, functional destruction of microRNA may cause various diseases. From the above facts, recently genetic diagnosis, determination of disease types, prognostic prediction or development of pharmaceutical products using microRNA has been expected. In Europe and the United States, functional analysis of microRNA and application of microRNA to medical services have been tried. Furthermore, with respect to cancer and a malignant tumor, involvement of a cancer gene and a cancer suppressor gene in onset and progress thereof is known but involvement of microRNA in control thereof is also elucidated. MicroRNA is regarded to be involved in controlling all of expression, progress and metastasis of a tumor. There are some reports on development of a medicinal drug of a microRNA (for example, colon cancer cell proliferation inhibitor using miR-34; see Patent Document 1) using these; however, at present, the development thereof is extremely slow.